Just want to share a photo after my listening session with them, truly amazing sound! Very effortless sounding, smooth from top to bottom, and expansive soundstage!

Now I understand where the "sennheiser house sound" coming from.

There is no "Sennheiser sound". There's some tonal relationship between HD600/HE60/HE90 I guess, but the HE90 is much better than either of those. HE60 sounds a lot like a less veiled and faster HD600 but both sound a bit sterile compared to the HE90. HE90 has a much bigger soundstage and smoother treble among other positives. Glad you enjoyed listening to it, it's an incredible headphone.

There is no "Sennheiser sound". There's some tonal relationship between HD600/HE60/HE90 I guess, but the HE90 is much better than either of those. HE60 sounds a lot like a less veiled and faster HD600 but both sound a bit sterile compared to the HE90. HE90 has a much bigger soundstage and smoother treble among other positives. Glad you enjoyed listening to it, it's an incredible headphone.

Well, for me the "sennheiser sound" is do exist as I have hear that type of sound in many of sennheiser products (not all of sennheiser line-up though). They don't share exactly same character (like the same amount of treble/mid/bass), but they have similiar presentation, so when I heard them, that "sennheiser sound" just comes to my mind.

Yeah I agree about the HE60, that's why it's a bit hard for me to liking it as I prefer darker sound, I prefer 007 than the "baby". I really curious about pair the HE60 to Orpheus amp.